Ferroelectric Properties of Colemanite

Abstract

The ferroelectric properties of the calcium borate mineral colemanite are investigated in the ferroelectric and paraelectric temperature regions. It is shown that Devonshire's phenomenological theory may be applied successfully to account for the experimental measurements of spontaneous polarization and electrical susceptibility over a wide temperature range. The thermodynamic transition is confirmed to be of second order occurring for unbiased crystals at −7°C. It is shown, in general, that the temperature τ₀ at which such a transition takes place depends upon the effective electric field E as τ₀ = kE^⅔ where k is a constant evaluated from Devonshire's expansion. The effect of space charge fields are evaluated and a comparison is presented between the ferroelectric properties of colemanite and those of KDP.